Monte Carlo calculated stem effect correction for NE2561 and NE2571 chambers in medium-energy x-ray beams.
Monte Carlo calculated stem effect correction for NE2561 and NE2571 chambers in medium-energy x-ray beams.
复制标题
蒙特卡罗计算了中能 X 射线束中 NE2561 和 NE2571 暗室的干效应校正。
DOI：
--
复制
发表时间：
1995
影响因子：
3.5
通讯作者：
A. Nahum
中科院分区：
文献类型：
--
作者：
C. Ma;A. Nahum
本文介绍了干效应校正因子的NE 2561和NE 2571电离室在空气中校准，并在一定深度的中能X射线束照射的体模中使用。空气中和体模中杆效应校正因子计算为不带和带室杆的电离室空气腔中吸收剂量的比值。然后将“全局”股骨柄校正因子计算为体模中校正因子与空气中校正因子的比值。计算进行了使用EGS 4（电子伽马簇射版本4）Monte Carlo代码系统连同使用相关的采样方差减少技术。结果表明，在一般情况下，腔室杆增加了腔室在空气中的响应，但降低了它在体模。对于NE 2571室，70 kV时的“全局”干效应校正系数为1.014 +/- 0.001（2.9 mm A1，0.1 mm Cu）至1.005 +/- 0.001（300 kV）（21.5 mm A1，5.1 mm Cu），而对于NE 2561腔室，对于相同的千伏和HVL值，其变化范围为1.039 +/- 0.002至1.010 +/- 0.002。在60 Co射束中，对于NE 2571室，全局杆校正为1.001 +/- 0.001，对于NE 2561室，全局杆校正为1.003 +/- 0.001。这与最近的实验结果一致。
This paper presents the stem effect correction factors for the NE2561 and NE2571 ionization chambers calibrated in air and used at a depth in a phantom irradiated by medium-energy x-ray beams. The in air and in phantom stem effect correction factors were calculated as the ratios of the absorbed dose in the air cavity of an ionization chamber without and with a chamber stem. The 'global' stem correction factor was then calculated as the ratio of the in phantom correction factor to the in air correction factor. The calculations were carried out using the EGS4 (electron gamma shower version 4) Monte Carlo code system together with the use of a correlated sampling variance reduction technique. The results show that in general the chamber stem increases the chamber response in air but decreases it in phantom. For an NE2571 chamber the 'global' stem effect correction factor varies from 1.014 +/- 0.001 at 70 kV (2.9 mm A1, 0.1 mm Cu) to 1.005 +/- 0.001 at 300 kV (21.5 mm A1, 5.1 mm Cu) while for an NE2561 chamber it varies from 1.039 +/- 0.002 to 1.010 +/- 0.002 for the same kilovoltage and HVL values. In a 60Co beam the global stem correction is 1.001 +/- 0.001 for an NE2571 chamber and 1.003 +/- 0.001 for an NE2561 chamber. This is consistent with recent experimental results.